Excavating machines, such as used in mining and construction operations, include buckets that are driven into the ground to gather a load of earthen material. The bucket is generally defined by a rear wall, a bottom wall and sidewalls to define a cavity with an open front for receiving the excavated material. The front edge of the bottom wall is provided with a lip on which ground engaging tools such as teeth, adapters and/or shrouds are generally attached to protect the lip against wear and to better break up the ground during digging. The lips are either formed of plate steel (which are called plate lips) or by a casting process (which are called cast lips). Either style of lip is welded into the bucket, i.e., to the front edge of the bottom wall and to the lower, front corners of each sidewall.
Cast lips are generally used on larger excavating machines such as dragline machines, cable shovels, face shovels, and hydraulic excavators. These lips are large steel structural members able to withstand the impact and other heavy loading experienced as the bucket is driven through the ground, resist undue wearing caused by the high abrasion environment, and securely support and hold the ground engagement tools in place for efficient digging. Accordingly, cast lips tend to be very heavy, which reduces the load each bucket can gather in each digging cycle. That is, excavating machines are designed for certain maximum loads, which include the weight of the excavated material as well as the weight of the bucket.
Existing lips typically have a structure that resists the many loads encountered in a digging operation and tends to carry the cantilevered tooth loads in torsion. The lips, however, tend to be massive and heavy to survive the very large loads and high abrasion environments commonly encountered in a digging operation and particularly in many mines. Mining and other excavating machines are constructed to lift loads up to a certain specified level. The more weight that exists in the lip, wear parts and other components of the bucket, the smaller the maximum payload that can be achieved by the bucket. The great size and weight also tends to increase manufacturing difficulties and cost of cast lips.